285. Endometrial lymphatics are reduced in the functionalis compared to basalis and myometrium

Information on uterine lymphatics is limited. The aim of this study was to characterise uterine lymphatic vessels and the corresponding growth factors in the endometrium and myometrium across the normal human menstrual cycle. Uterine tissues were collected from patients undergoing hysterectomy. Lymphatic and microvascular density (MVD/mm2) was determined on serial sections of full thickness uterus (n = 45) with antibodies to D2-40, CD31, CD34 and FVIII. Lymphangiogenic growth factors VEGF-C and VEGF-D immunolocalisation was also determined on serial sections. VEGF-C, VEGF-D and lymphatic endothelial cell markers VEGF-R3 and D2-40 protein expression was determined on protein extracted from myometrium and endometrium and separated by SDS-PAGE from proliferative (n = 5) and secretory (n = 5) hysterectomy specimens. The lymphatic vessels were closely associated with smooth muscle cells of spiral arterioles and VEGF-C and VEGF-D were primarily localised in the endometrial glands, luminal epithelium and myometrial smooth muscle bundles. The lymphatic MVD was significantly reduced in the functionalis (15.1 ± 2.3mm2) compared to basalis (80 ± 11.4mm2) and myometrium (63 ± 9.2mm2). Overall, lymphatics constituted 12% of all vessels in the functionalis, 60 % in the basalis and 30% of the myometrium. D2-40 positive uterine lymphatics showed considerable heterogeneity, with 88% co-localisation with the blood vessel marker CD31, but only 46% expressing CD34 and 31% with FVIII. Protein expression of VEGF-C, VEGF-D, VEGF-R3 and D2-40 were significantly reduced during the proliferative phase compared to the secretory phase and were also significantly reduced in the endometrium compared to the myometrium across the cycle (P ≤ 0.05). Endometrial functionalis lymphatics are reduced in conjunction with a reduction in lymphangiogenic growth factors compared with the myometrium.